Acantholysis is seen in all of the following except – a) Pemphigusb) Bullous pemphigoidc) Steven–Johnson syndromed) Toxic epidermal necrolysis

**Core Concept**
Acantholysis refers to the loss of intercellular connections between keratinocytes, leading to the separation of epidermal cells. This is a hallmark feature of certain autoimmune and blistering skin disorders.

**Why the Correct Answer is Right**
Bullous pemphigoid is a chronic autoimmune skin disease characterized by the presence of autoantibodies against components of the basement membrane zone. However, acantholysis is not a primary feature of bullous pemphigoid; instead, it is characterized by the formation of subepidermal blisters. Acantholysis is a feature of pemphigus, where autoantibodies target desmoglein proteins, leading to the disruption of intercellular connections between keratinocytes.

**Why Each Wrong Option is Incorrect**
**Option A:** Pemphigus is characterized by acantholysis due to the presence of autoantibodies against desmoglein proteins, making it an incorrect choice.
**Option B:** Bullous pemphigoid is characterized by subepidermal blisters, not acantholysis, making it an incorrect choice.
**Option C:** Stevens-Johnson syndrome is a severe skin and mucous membrane disorder that can be triggered by medications or infections, and acantholysis can be seen in some cases, making it an incorrect choice.
**Option D:** Toxic epidermal necrolysis (TEN) is a severe skin condition that can be triggered by medications, and while it is often associated with epidermal necrosis, acantholysis can also be seen in some cases, making it an incorrect choice.

**Clinical Pearl / High-Yield Fact**
Acantholysis is a key feature of pemphigus, and the presence of autoantibodies against desmoglein proteins can be used as a diagnostic marker.

**Correct Answer: B. Bullous pemphigoid.**